The present invention relates to an exterior autobody part of reinforced plastic, intended to be mounted on a motor vehicle. The expression xe2x80x9cexterior autobody partxe2x80x9d refers to the part being entirely or partly visible when the motor vehicle is viewed from the outside.
The invention further relates to a method and an arrangement for forming such an exterior autobody part.
The invention pertains to the fields of reinforced thermoplastic composites or laminates and vacuum forming of thermoplastic components.
The exterior autobody part according to the invention comprises a number of functional layers, intended to provide the properties which are required for the application. Examples of such properties are low weight, high stiffness and durability, recyclability and visual properties.
The invention can be applied within the field of motor vehicle components which are visible from the exterior of the vehicle, for example boot lids or wind deflectors.
Within the field of sports equipment, a vacuum forming process is previously known for manufacturing thermoplastic articles, for example wind-surfing boards. The process utilizes two sheet-shaped material batches which are clamped in a clamping device and is therefore usually called xe2x80x9ctwin-sheetxe2x80x9d. The two braced material batches are heated and comprise thermoplastic material and, during the forming, function as elastically stretchable membranes which, by means of external vacuum and/or internal pressure acting on the membranes, are formed according to the inner contours of an enclosing, cooled forming device. By means of this previously known forming process, different hollow plastic articles which comprise thermoplastic material can be obtained.
Within the field of conventional exterior autobody parts for motor vehicles, for example boot lids, autobody parts of body panel sheets or, for example, of glass-fibre reinforced thermosetting plastic are previously known.
Conventional exterior autobody parts of sheet metal are manufactured through different metal working operations comprising rolling, pressing, bending and welding. Such sheet metal parts usually also comprise separate reinforcements in the form of stiffening profiles and similar components, which are manufactured and mounted in separate steps.
After the forming and/or mounting of a conventional exterior autobody part of sheet metal, different surface finishing and polishing steps follow in order to provide the finished autobody part with aesthetically pleasant and corrosion-protected surfaces on both the inside and the outside of the autobody part.
Where previously known exterior autobody parts of glass-fibre reinforced thermosetting plastic or other thermosetting plastic composites are concerned, such parts are manufactured in a process with several forming or laminating steps with the use of reinforcement material, for example glass-fibre mats, and thermosetting matrix material, for example vinyl ester resin. After the forming of the reinforcement material and the impregnation thereof with thermosetting matrix material, a relatively time-consuming curing follows which, for instance, may take place within a moulding or pressing tool. Thereafter, the exterior autobody part of reinforced thermosetting plastic generally has to be surface-finished and polished further in order to obtain surfaces with a surface finish of sufficient quality for the application.
The above-mentioned, previously known, exterior autobody parts can be perceived as having certain disadvantages. Where autobody parts of conventional sheet metal are concerned, it may be difficult to achieve a sufficiently low autobody part weight in order to fulfil the ever increasing demands upon low fuel consumption and low emissions to the environment which are placed upon the motor vehicles of today. Furthermore, separate surface finishing and surface polishing lines are required in order to provide material surfaces with the desired properties to the finished sheet metal parts.
Where parts of glass-fibre reinforced thermosetting plastic are concerned, the relatively time-consuming thermosetting process, and the demands for separate surface finishing and polishing steps, may be perceived as difficult. Furthermore, it is difficult to recover and recycle composite materials of thermosetting plastic.
Accordingly, the first object of the present invention is to provide an exterior autobody part of reinforced plastic, intended to be mounted on a motor vehicle, which part is recyclable in a simple way and which, without any separate reinforcements and in spite of low weight, provides sufficient stiffness and durability, and which does not require any time-consuming curing when manufactured.
This object is achieved by means of the exterior autobody part according to the invention comprising load-bearing layer(s) and surface layer(s) and that the load-bearing layer(s) comprise(s) fibre-reinforced thermoplastic which forms internal cavities and/or that one or several recesses has/have been created in the surface layers and the load-bearing layers, and that the surface layer(s) and the load-bearing layers(s) together with cavities and/or recesses provide a load-bearing material structure.
A second object of the present invention is to provide an autobody part of reinforced plastic, intended to be mounted on a motor vehicle, having a surface finish with a sufficient quality in order not to require any special surface finishing in the form of grinding or the like before painting, or which provides a surface finish of a sufficient quality in order to be left unpainted.
This object is achieved by means of the exterior autobody part according to the invention providing at least one decorative layer, between surface layer and load-bearing layer, and that the surface layer(s) and the decorative layer(s) together provide at least one external surface which provides the main portion of the visual effect and the surface properties which the exterior autobody part should exhibit when mounted on a motor vehicle, and that surface layers, decorative layers and load-bearing layers all comprise a thermoplastic and have been formed together under heating.
A third object of the present invention is to provide an arrangement for forming an exterior autobody part according to the invention.
This object is achieved by means of the arrangement according to the invention comprising a forming tool with tool halves, arranged to be opened and closed in order to create an internal form cavity, and that the arrangement comprises material holders intended for clamping at least one material batch with thermoplastic material, heating means for heating the material batch, pressurizing connection and vacuum connection intended to generate, by means of internal pressurization and external vacuum application, a forming force on the material batch functioning as a stretchable membrane after heating, and cooling means intended to cool down the heated material batch after forming inside the form cavity, and that the material batch comprises at least one load-bearing layer with reinforcement fibres.
Furthermore, a fourth object of the present invention is to provide a simple and effective method for forming an exterior autobody part according to the invention.
This object is achieved by means of the method according to the invention comprising the use of a forming tool with first and second tool halves arranged to be opened and closed in order to create an internal form cavity, and that thereby at least one material batch with thermoplastic material is clamped between the tool halves in an open position by means of material holders, after which the material batch by means of heating means is heated to or above the softening temperature of the thermoplastic material, that the tool halves are thereafter closed around the material batch while a vacuum is applied between the material batch and the first tool half, wherein the material batch functions as a stretchable membrane and is formed according to the internal surface of the first tool half, after which cooling means in the tool halves gradually cools down the material batch to a temperature below the softening temperature, that the tool halves are brought into an opened position and that thereafter a blank is removed from the forming tool in order to provide, after trimming and making of holes, an exterior body part of reinforced plastic with a load-bearing structure.